1. Field of the Invention
This invention relates to a method for gasifying solid organic materials to convert the chemical energy stored in such materials to thermal energy. More particularly, this invention relates to a method for gasifying biomass materials, such as wood chips, sawdust, corn cobs, bagasse, tobacco waste and the like. The invention utilizes a new and improved feed hopper with inclined reciprocating plates lying along the bottom of the feed hopper to prevent the feed material from jamming in the hopper, even when the feed stock is moist and/or irregularly or nonuniformly shaped, and it utilizes a domed catalytic oxidation chamber where the feed stock is partially oxidized at an elevated temperature. The high-temperature gases produced by the practice of the invention can be utilized to advantage, for example, as the thermal energy source for a conventional water tube boiler.
2. Description of the Prior Art
It has long been recognized that many industrial and agricultural solid organic by-products, such as wood chips, sawdust, corn cobs, bagasse, tobacco waste, and the like, contain large amounts of chemical energy. The substantial increases in the cost of traditional fuels, such as fuel oil and natural gas, which took place during the 1970's, have provided substantial economic incentive to try to develop effective and efficient techniques for recovering the energy in these organic by-products, energy that traditionally was not recovered to any substantial extent. Such organic materials, which are frequently referred to as "biomass" materials, are now successfully utilized to some extent as fuel in some very large industrial systems, for example, in firing the recovery boiler in a pulp or paper mill. However, the high capital cost which has heretofore been associated with biomass energy recovery systems has precluded their successful use in small or even medium size energy recovery systems. Medium size energy recovery systems, viz., of the size from about 4,000,000 to 8,000,000 BTU/Hr., are used in schools, nursing homes, and small industrial and commercial establishments and, to date, biomass fuels have not been satisfactorily utilized as fuel in heating systems for such facilities. Among the U.S. Patents that have been issued on inventions relating to the recovery of energy from wood chips or similar organic materials are U.S. Pat. No. 4,184,436, to Palm, et al.; U.S. Pat. No. 4,312,278, to Smith, et al.; U.S. Pat. No. 4,366,802, to Goodine; U.S. Pat. No. 4,321,877, to Schmidt, et al.; and U.S. Pat. No. 4,430,948, to Ekenberg. However, it is not known that any of the inventions described in these patents have been successfully adapted to recover biomass energy on a cost-effective basis in small and medium size energy recovery systems.